Historically, Helicobacter pylori (H. pylori) was found to be difficult to eradicate using known chemotherapeutic agents. Although many antibiotics can suppress H. pylori growth in vivo, the mucosal concentration appears to be inadequate and penetration of the usual gastric mucus layer is poor. Furthermore, there is frequently more than one infecting agent within the mucosa and hence, sensitivities of the various bacteria may vary within one patient and within one region of the mucosa. The development of adequate in vivo eradication methods for chronic H. pylori infection has therefore been difficult.